Voltage to current converter circuits generally provide a linear transformation of an input voltage level to an output current level for use in applications in which a current level signal rather than a voltage level signal is required as an input signal to another circuit. 12 In prior art voltage to current converter circuits the input voltage range over which the circuit is linear is usually significantly less than the power supply voltage levels used by the voltage to current converter circuit. This linear range of input voltage (referred to herein as the dynamic range of the circuit) limits the input voltage range which can be used with these prior art circuits. While the input voltage signal can be scaled down and the corresponding output current increased to compensate for the decreased input voltage range, this scaling down and reamplification changes the transconductance of the circuit, which can be undesirable in some applications.
In addition, there are applications in which a bidirectional output current is required. In a bidirectional output current, the voltage to current converter is capable of either supplying (sourcing) current or receiving (sinking) current.
Therefore, it can be appreciated that a voltage to current converter which has an extended dynamic range and which is also bidirectional is highly desirable.